There are tons. Which ones stick out in your mind?
Number one for me will probably always be the death of Wolfwood in the Trigun anime. His death was okay in the manga, but it lacked the emotional impact of Nicholas dragging himself into a chapel and dying as he confesses his desire to live. The music was also spot-on.
A somewhat-distant but still strong second is Gohan's transformation to SSJ2 in DBZ. I knew nothing of the Cell Saga when I first found the clip of that moment online, and watching him flip out sent shivers down my spine.